A fancy vivid pink diamond that is believed to have been part of the collection of Napoleon Bonaparte’s niece, Princess Mathilde, could fetch up to $18 million when it hits Sotheby’s auction block next month.Dubbed the “Historic Pink Diamond,” the diamond is an 8.72-carat stone, VS2 clarity and is a non-modified cushion cut; unusual for a pink diamond.

Scheduled for May 12 Sotheby’s auction of Magnificent Jewels and Noble Jewels, in Geneva.